science

As far as I’m aware NO~2~ will fill a pit. In the industry I work in NO~2~ leaks are serious threat because the engines that are worked on are in, what is essentially, a cage that you walk down into. I’ve not experienced it myself but heard from someone who experienced it firsthand as you just start feeling sleepy. I know now that it’s because our bodies are sensitive to asphyxiation from CO~2~ but not NO~2~, so as it displaces the oxygen in our lungs you just start getting woozy and tired.

All that being said; I am not an expert. Half this is information from diesel mechanics who work with it and the other half is from random science videos. So take it with a grain of salt.